Method and apparatus for treating a layer of bulk material

ABSTRACT

The invention includes a method and an apparatus for treating, in particular cooling, a layer of bulk material by means of a stream of gas passed through it on a grate. The grate includes a plurality of elongated planks which extend in a conveying direction and are driven in advancing and return strokes in the conveying direction in such a manner that at least two adjacent planks are moved forwardly simultaneously and are moved backwardly non-simultaneously. Since the material located on a plank which is being moved back is prevented from completely following the plank moving back by the friction generated with the material located above the adjacent planks or with the wall, the conveying effect in the conveying direction outweighs the conveying effect in the opposite direction.

REFERENCE TO RELATED APPLICATION

This application is a division of Ser. No. 10/459,709, filed Jun. 12,2003.

FIELD AND BACKGROUND OF THE INVENTION

It is known to treat a bed of bulk material with gas by conveying itcontinuously over a grate so that the gas flows through it. To coolcombustion material, for example cement clinker, it is customary to usewhat are known as pusher grates, which comprise overlapping rows of, inalternation, stationary grate plates and grate plates which are movedforward and back in a conveying direction (DE-A 3 734 043). The grateplates are used to blow cooling air into the bed of material, and thisair is discharged above the bed of material in order for the heat to berecovered. For economic operation, pusher grates require complexmounting of the moving parts and are also complex since they arecomposed of relatively small parts. Another known design of grate makesuse of a stationary, air-permeable supporting base, over which the layerof material is moved by means of scrapers which are moved continuouslyin the conveying direction or by means of reciprocating pusher members(EP-A 718 578; DE-A 10018142). The scrapers or pusher members have to beguided moveably through the grate surface from below, which is a complexarrangement. Moreover, they are exposed to high levels of wear withinthe hot layer of material. The passage of air is impeded and the coolingaction restricted in the region of the grate in which they and theirdriving and sealing members are located. Yet a further type of cooler(DE-A 101 13 516) uses a large-area grate which is moved forward andback in its entirety, the bed of material being held in place by ablocker plate arranged at the start of the grate during the returnstroke, so that the grate can slide beneath the blocker plate. This hasthe drawback that the grate length which can be utilized is limited onaccount of the barrier formed by the blocking action.

Working on the basis of the above prior art, the invention is based onthe object of providing a method and an apparatus for treating, inparticular cooling, a layer of bulk material which rests on a grate andhas a stream of gas passing through it, which promise a simple structureand simple operation as well as uniform treatment of material even witha considerable grate length.

SUMMARY OF THE INVENTION

The method according to the invention uses a grate which comprises aplurality of planks which are elongate in the conveying direction. Aplurality of these planks are moved forward and back in the conveyingdirection in order to move the material in the conveying direction. Themovement is controlled in such a way that each individual plank in eachcase moves forward in the conveying direction together with at least oneadjacent plank and in each case moves back at a different time from theadjacent planks. In this case, the width of the planks is made so narrowthat during the backward movement of a plank the backward conveyingaction exerted on the material above it, which is based on the frictionbetween the plank in question and the material, is lower than theforward conveying action or holding action which is based on thefriction exerted by the respectively adjacent material or by the sidewalls. The result of this is that when a plank moves back between twostationary planks, the strip of material above it is mostly orcompletely held in place by the material located above the adjacentplanks, and consequently to this extent does not follow the plank whichhas been moved back individually. When two or more adjacent plankstogether with the material located thereon move simultaneously in theconveying direction, surrounding an individual plank which is stationaryor moving in the opposite direction, they also carry with them the or atleast a significant part of the strip of material located on the latterplank. By suitable movement control, in which the return stroke of eachplank is controlled in such a way that the adjacent planks hold thematerial located thereon in place while the forward stroke is alwayscarried out by a plurality of adjacent planks simultaneously, the bed ofmaterial is conveyed in the conveying direction.

This conveying principle has long been known (DE-B 1 296 087, U.S. Pat.No. 3,534,875, U.S. Pat. No. 4,144,963). In the field of conveyingtechnology, this principle does not play a major role, since it isgenerally simpler for the layer of material to be moved by means ofpusher members or scrapers which move above the supporting surface. Bycontrast, in the context of the invention it constitutes a particularadvantage, since there are no conveying members above the grate whichwould be exposed there to the possibly aggressive action of thetreatment atmosphere or the material.

A further advantage of the invention consists in the fact that themixing action exerted on the bed of material by the conveying movementis low. In particular, there is a lack of vertical mixing movement inthe bed of material. The result of this is that in the case of a coolingprocess the treatment gas passes through the hottest layers last and theresult is an improved recovery of heat compared to what is possible withmore lively vertical mixing of the bed. Corresponding statements canalso be made with regard to other types of heat or mass transfer.However, if a more intensive movement of material is desired, forexample in order to avoid caking, this can be brought about by theforward conveying not taking place uniformly over the entire width ofthe grate, but rather in sections, so that a relative movement isgenerated between these sections. Another possible way of moving thematerial to a greater extent consists in selecting a higher gratefrequency. Finally, a movement within the bed of material can beproduced by stationary internals which project into the bed.

The return stroke is expediently faster than the forward stroke.Furthermore, it may be expedient if the plurality of planks constantlymoves at the same speed in the conveying direction. This makes itpossible to ensure that the layer of material always moves at asubstantially constant speed without energy losses or disruptive shakingbeing produced by coming to a standstill and starting up again.

In the case of a combustion material cooler, it may be expedient for atleast one plank close to the edge to be moved at a lower frequencyand/or amplitude than the planks located further toward the inside, inorder in this way to prevent the material at the edge of the bed fromflowing undesirably quickly. Instead or in addition, it is possible toprovide stationary edge planks. It is also possible for the other movingplanks to be controlled differently with regard to frequency andamplitude, so that it is possible to take account of different demandsimposed on material over the width of the grate. Specifically, dependingon the nature of the combustion furnace connected upstream of the coolerand/or of the furnace discharge, it is possible that the properties ofthe material will not be uniform over the width of the bed. In ordernevertheless to achieve a conveying speed which is identical or,depending on circumstances, deliberately different, it may therefore bedesirable for the conveying movements of the planks in one part of thegrate to be more intensive than in another part of the grate. Adifferent conveying action on the part of the planks can also beachieved by some of them from time to time not participating in thestroke of the planks which are otherwise moved with them. By way ofexample, it is possible to provide for a plank to participate only inevery other conveying stroke of the adjacent plank or for it to miss outon every seventh conveying stroke.

Finally, it is also possible to arrange suitable brakes which are formedby stationary obstacles in regions in which experience has shown thatthe material tends to reach higher speeds or even to shoot straightthrough. By way of example, stationary intermediate planks, which ifappropriate may also be provided with flow obstacles projecting into thebed of material, may be provided between adjacent planks. It is alsopossible for internal fittings which project over the grate from theside walls to be provided, so that the uniform structure of the basedoes not have to be disrupted by internal fittings. The internalfittings which project over the grate from the side could have a heightwhich is lower than the normal bed height, so that they constantlyengage in the bed in order to prevent its edge regions from flowing morequickly. If it is merely necessary to prevent material above the normalbed from shooting straight through, their height is selected in such away that they are located where such a phenomenon is to be expected,i.e. above the normal bed height.

The gap between adjacent planks is expediently sealed in order toprevent material from dropping through the grate and/or to prevent gasfrom passing through. The seal used is preferably a labyrinth seal inwhich a longitudinal strip which is secured to the edge of the plank isimmersed in a bed of the material which is held by the adjacent plank ora special channel. A simple design of this principle is known (U.S. Pat.No. 5,222,593), in which an edge strip projects upward from the edge ofone plank and an edge strip which projects downward from the other plankengages over it. In this case, however, the seal is located in theaggressive region of the material which is to be treated. Therefore,according to the invention preference is given to an embodiment in whichthe sealing arrangement is arranged beneath the planks. In this case, alongitudinal channel which is open at the top and in operation receivesa bed of the material is arranged in a stationary position at the edgeof one plank or separately. A longitudinal strip projects from the edgeof the plank into this channel and into the bed which forms therein.Together, these parts form a seal preventing bulk material which entersthe channel through the gap located between the planks from passingthrough. Moreover, the arrangement forms a seal or at least one flowobstacle to gas between the space beneath the grate and the space abovethe grate. A limited passage of gas may be desirable, so that thedesired gas treatment in the bed of material can also take place abovethis sealing device. For this purpose, it will in many cases besufficient for one side of the upwardly open channel to be connected tothe space beneath the grate.

According to a particular feature of the invention, the sealing deviceor a stationary intermediate plank located between two adjacent planksis supported by a stationary wall which separates the spaces beneath thegrate below the adjacent planks from one another. This enables thematerial located on adjacent planks to be ventilated to differentextents.

During operation, the strip which projects downward into the channelfrom the edge of a plank should always maintain a sufficient spacingfrom the channel walls, so that the material is not crushed between thestrip and a channel wall. This can be achieved by making the lateralspacing between the strip and the channel walls greater than the lateralguide clearance of the planks including any thermal expansion.Furthermore, for the same purpose it may be expedient for the gapbetween the bottom edge of the strip and the base of the channel to besmaller than the gap between the strip and the channel wall.

If the channel is provided in a stationary position, a longitudinalstrip may project downward into this channel from each of the two plankedges which are to be sealed with respect to one another. However, it isalso possible for the channel to be connected to the edge of one plankand for the downwardly projecting strip to be connected to the edge ofthe other plank.

That part of the channel which is in direct communication with the plankgap will generally be completely filled with bulk material. During therelative movement of the strip and the channel with respect to oneanother, some bulk material will also pass through to the other sidebeneath the strip. The vertical spacing between the lower edge of thestrip and the channel base should be small, so that this passage ofmaterial is inhibited. Moreover, the channel walls should be high enoughto reliably prevent the material from overflowing into the space beneaththe grate. An overflow of this type is unlikely because the channel isconstantly emptying itself. Because the strips of adjacent planks aremoved forward together and back individually, the bed of materiallocated in the channel will be moved to a greater extent in theconveying direction than back and will be pushed out of the end of thechannel, which should be open for this purpose. Since there is no riskof the material moving backward, the rear end of the channel, adjacentto the feed end of the grate, can be open.

It is customary to connect a short section of grate whose feed surfaceis particularly suitable for direct feed of the material which drops outof the furnace and which is consequently referred to as a feed sectionupstream of the grate of a combustion material cooler. During theirmovement, the feed-side ends of the planks of the grate sectionaccording to the invention move more or less far under the feed section.For the relative movement, they require a certain clearance betweentheir top side and the underside of the feed section. To prevent coolair from entering the bed of material from the space beneath the grate,which is under excess pressure, as a result of this clearance withouthaving flowed through and cooled the grate, it is expedient to provide asealing arrangement in the region of which this clearance is reduced.

Advantageously, the top side of the grate is provided over substantiallyits entire surface with hollows in which cooled material collects,preventing direct contact between the grate and hot layers of material.The feed-side ends of the planks are expediently also equipped withhollows of this type. When they move under the feed section of thecooler and there is no longer any load from the bed of material at thatlocation, there is a risk of the treatment gas which penetrates into thehollows from below blowing out the contents of the hollows or at leastthe fine material. According to a further feature of the invention,therefore, there is provision for the air passage openings in thehollows to be blocked off from the supply of air when they are locatedbeneath the feed section of the cooler.

An important advantage of the invention consists in the fact that thewear to the grate and its bearing members does not impair its function.Therefore, the bearing members can be of simple configuration. By way ofexample, the grate may be mounted on rollers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below with reference to thedrawing, which illustrates an advantageous exemplary embodiment. In thedrawing:

FIG. 1 shows a diagrammatic longitudinal section through a combustionmaterial cooler,

FIG. 2 shows diagrammatic partial plan views of the cooling grate of afirst embodiment in various stages of operation,

FIG. 3 shows plan views corresponding to FIG. 2 of a second embodiment,

FIG. 4 shows a partial longitudinal section through a first embodimentof the cooler,

FIG. 5 shows a longitudinal section, corresponding to FIG. 4, through asecond embodiment of the cooler,

FIG. 6 shows a cross section through a cooler,

FIG. 7 shows a partial section through a sealing arrangement on a largerscale,

FIG. 8 and FIG. 9 show further exemplary embodiments of sealingarrangements,

FIG. 10 and FIG. 11 show a cross section and an isometric illustrationof a further embodiment,

FIG. 12 shows a further form of the seal,

FIG. 13 shows details of the seal between the grate sections, and

FIG. 14 shows a variant of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with FIG. 1, a cooler housing 1 forms a feed shaft 2within which the end of a rotary tubular kiln 3 opens out. In the feedshaft 2, the material 8 drops onto a feed section 4 of the cooler, fromwhere it passes onto the grate section 5 which is formed and operated inaccordance with the invention. Where the following section, without anyadditional definitions, refers to the grate, this term is to beunderstood as meaning the grate section. The possibility of differentlydesigned grate sections following or being connected upstream of thisgrate section should not be ruled out. The grate 5 is arrangedsubstantially horizontally. It can be arranged with a slight downwardgradient, in order in this way to increase the resistance which preventsthe material from following a grate plank as the latter moves back. Onthe other hand, this makes it easier for the material to move in theconveying direction and reduces the amount of energy required for theconveying. However, the grate 5 may also be laid such that it risesslightly if it is important to prevent the possibility of relativelyfree-flowing material shooting straight through (the “Red River”phenomenon). At the end of the grate 5, the material can be dischargeddirectly or via a further grate section 6, for example to a crusher 7.

The grate 5 is composed of a plurality of planks 10 arranged paralleland next to one another. Examples with three and five planks arediagrammatically depicted in FIGS. 2 and 3, respectively. Successivefunctional phases illustrate the sequence of movement of the plankstherein.

FIG. 2 a illustrates all three planks 10 in their position which isfurthest advanced in the conveying direction 11. Their forward movementstops in this position. Then, they are moved back individually, asillustrated in FIGS. 2 b, c and d. As soon as they have all adoptedtheir fully retracted position indicated in FIG. 2 d, they start thejoint forward stroke again until they have once again reached theposition shown in FIG. 2 a. During the common forward stroke, they carrywith them the bed of material located on them. When the planks are movedback individually, by far the majority of the material located on themcannot follow this movement, since it is held in place by the frictionwhich is exerted on it by the material which is located on the adjacentplanks and/or by the side walls. In the case of the sequence of movementillustrated in FIG. 2, it is assumed that during the movement phase inwhich the planks are being moved back individually the other planks arein each case stationary.

By contrast, the sequence of movements illustrated in FIG. 3 is based onthe assumption that all the planks with the exception of in each caseone plank, which is being moved back, are moving uniformly forward. FIG.3 a illustrates the state in which the plank 10.1 which has just beendrawn back is in its rearmost position, while the plank 10.5 has reachedits furthest advanced position. During the time between this figure andthe next state illustrated in FIG. 3 b, all the planks 10.1 to 10.4 moveslowly forward synchronously while the plank 10.5 is drawn back into therear starting position. In the next phase leading up to state 3 c, theplanks 10.1 to 10.3 and 10.5 move a step forward while the plank 10.4 isdrawn back into the rear starting position, and so on. If the forwardmovement is to be continuous, in this example the backward movement mustbe at least five times as quick as the forward movement.

In the examples shown in FIGS. 2 and 3, it has been assumed that all theplanks have identical rates of advance. This is not necessary. Rather,the advancing speed of the individual planks can be controlleddifferently or may be set differently from the outset. By way ofexample, there are the abovementioned technical grounds for moving theplanks 10.1 and 10.5 close to the edges more slowly than the plankswhich are closer to the center.

Furthermore, in the examples it has been assumed that the planks aremoved back individually. However, it is also possible for two planks tobe retracted simultaneously when they are at a sufficient distance fromone another and the other planks are sufficient to hold the materiallocated above the planks being retracted in place. By way of example, inthe example shown in FIG. 3 it would be possible for the planks 10.1 and10.4, on the one hand, and the planks 10.2 and 10.5, on the other hand,in each case to be retracted simultaneously. This applies both to thecontinuous procedure which has been explained with reference to FIG. 3and to the discontinuous procedure which has been explained withreference to FIG. 2.

In FIGS. 2 and 3, it has been assumed, for the sake of simplicity, thatthe planks directly adjoin one another at the walls of the coolerhousing 1. This is not necessarily the case. By way of example, if thegrate is arranged inclined downward, it may be expedient for stationarystrips or planks to be arranged between the individual moving planks,having the effect of decelerating the material in order to prevent itfrom shooting straight through. Furthermore, with a horizontal ordownwardly inclined arrangement of the grate, it may be appropriate tohold in each case one edge strip which directly adjoins the walls 1 in astationary position.

Internal fittings can be used to additionally increase the resistanceimparted to the material with regard to movement in the oppositedirection to the conveying direction. By way of example, it is possiblefor the spacing between the side walls of the cooler housing 1 orbetween additional internal fittings to taper in the opposite directionto the conveying direction 11.

The planks 10 include air passage openings 12 in a distribution which isas uniform as possible. Experience gained from other types of coolinggrates also applies to the formation and arrangement of these openings.In accordance with FIGS. 4 and 5, hollows 14 on the top side of theplank are divided from one another by transverse walls 13 and aredimensioned in such a way that bulk material is retained therein. Thisforms a protective layer with respect to the hot and abrasive bed ofmaterial located above. This is also known from other types of cooler.

The hollows 14 can be dispensed with if the material is relativelyunabrasive or if the surface of the planks 10 is made sufficientlywear-resistant. In this way, it is possible to influence the coefficientof friction between grate and material. This can also be achieved in adifferent way by means of the width of the grate if it is desired forthe material in certain areas of the width to be influenced to a greaterextent by the friction of the adjacent material than by the plank below.

In FIGS. 4 and 5, it has been assumed that the space 17 beneath thegrate is subject to excess pressure and as a result the cooling air isforced from the space beneath the grate through the grate openings 12and through the bed of material 8. To ensure that any particles whichdrop down through the grate openings 12 do not pass into the space 17beneath the grate, catching profiled sections 18, which catch thematerial which drops through the grate and allow it to be returnedupward into the bed by the flow of air, are located beneath the openings12.

Instead of the grate being ventilated by excess pressure in the spacebeneath the grate, it is also possible for the planks in their entiretyor in sections to be connected to compressed-air sources via flexiblepassages. This provides the option of providing the bed of material withdifferent levels of ventilation in different areas across the width andalong the length.

The planks 10 may be mounted on rollers 15. They are connected to adrive (not shown) which enables them to be advanced in the conveyingdirection 11 and then retracted again.

The sectional view shown in FIG. 6 presents the cross section throughthree planks 10 in the cooler housing 1, the top side of which planks isformed by the hollows 14 divided up by walls 13 and on which planks thebed of bulk material 8 rests. Moveable components are provided withhatching which starts at the bottom left and runs to the top right,while stationary components are provided with hatching which runs fromthe top left to the bottom right. The width 9 of the individual planksis such that the movement of that part of the layer of material 8 whichis located above them in the conveying direction and/or in the oppositedirection to the conveying direction is determined to a greater extentby the friction from the adjacent areas of material or the walls 1 andby the associated plank 10. More specifically, it is impossible toprevent a part of the material located close to the plank surface (forexample the area below the dot-dashed line 30) from participating tosome degree in the movement of the plank, depending on the distance fromthe plank. However, a large proportion of the material located above theplank will not participate in the return movement of the plank if theadjacent planks are stationary or are being moved in the oppositedirection.

The higher the bed of material compared to the plank width, the greaterthe influence of the friction of the adjacent material or of the coolerwall on the material located above the plank compared to the influenceemanating from the friction of the plank. Consequently, the efficiencyof conveying increases as the ratio of the bed height to the plank widthincreases. The method is expediently operated in such a way that thisratio is no less than 0.7, preferably no less than 0.9, or the plankwidth is selected in such a way to be no greater than the reciprocal ofthis number, based on the projected bed height. It is preferable for theratio of bed height to plank width to be in the range from 1 to 1.2.

Between the planks 10 or between the planks close to the edge and thewall 1 there is a gap 31, through which material can penetrate downward.In a stationary position beneath the gap 31 there is a channel 32 withwalls 33 which receives the material which drops through. At the planks10, close to their edges, there is in each case one downwardlyprojecting strip 34 which is immersed in the channel 32 and the bottomedge of which is at only a short spacing from the base of the channel32. The material, which in FIG. 7 is indicated by cross-hatching,therefore cannot pass without resistance into the space 35 between thechannel walls 33 and the strips 34. The arrangement described representsa seal preventing material from passing through the space 17 beneath thegrate.

The ratio between the spacing formed between the lower edge of the strip34 and the base of the channel 32 and the height of the material in thegap 35 between the strip 34 and the wall 33 of the channel 32 is ofconsiderable importance for the sealing function. The height of this gapis expediently 3 to 20 times the abovementioned spacing, more preferablyapproximately 8 to 12 times as great. In an exemplary embodiment whichhas proven successful, the spacing between the lower edge of the strip34 and the base of the channel 32 is 2-5 mm and the height of the wall33 is 80 mm.

If the resistance to which the material is subject as it passes throughthis sealing arrangement should in specific instances be insufficient,the channel 32 can be pressed upward by spring force, so that the baseof the channel bears against the lower edge of the strips 34substantially without any gap. However, this measure will not normallybe necessary, since the material which passes through the gap 31 intothe channel 32 is continuously conveyed out of the channel in thelongitudinal direction. The conveying principle means that the strips 34will never be moving simultaneously in the opposite direction to theconveying direction within the stationary channel 32 but always movessimultaneously in the conveying direction. Consequently, the conveyingeffect which is exerted on the material located in the channel 32 in theconveying direction is stronger than the conveying effect in theopposite direction. The channel 32 is open at its delivery-side end, sothat the material can drop out at that end. If, depending on thearrangement of the grate and the type of material, it should emerge thatmaterial also drops out of the channel 32 at the feed-side end of thegrate, suitable collection features (chamber 30) or seals can beprovided at that end preventing the material from escaping. However, thefact that the material is conveyed in the conveying direction in thechannel means that this measure will not normally be required.

The lateral spacing between the walls 33 and the strips 34 is selectedin such a way that they do not under any conditions make contact withone another or come so close to one another that the material locatedbetween them is crushed. Accordingly, the spacing between them should begreater than the expected lateral displacement of the strip 34 caused bythe movement clearance of the plank and the thermal expansions.

The risk of the material being crushed between adjacent planks can bereduced by their opposite side walls 36 enclosing a gap which widensupward in the shape of a wedge, in accordance with the exampleillustrated in FIG. 8. This prevents the material from becoming jammedin the gap, which could lead to the planks being lifted up.

According to a further exemplary embodiment, which is shown in FIG. 9,the strip 34 is arranged at the edge of a plank and the channel 32 whichinteracts in a sealing manner therewith is arranged at the edge of theadjacent plank, beneath the latter.

Yet another exemplary embodiment for the sealing between adjacent planksis shown in FIG. 14. A U-shaped profiled section 70, which bears a sidewall 71, is secured continuously in the longitudinal direction to theedge of the plate 10 which can be seen on the left-hand side of thedrawing. This wall 71 laterally delimits the hollows (number 14 in FIGS.4 and 6) which are formed by transverse webs 13 above the planks 10. Theplanks 13 are continued by 13 a above the U-shaped profiled section 70.

The side wall 71 forms a downwardly projecting limb 34 which projectsdownward into the bed of material formed on the adjacent plank 10 (onthe right-hand side in the drawing) and interacts with a wall 33 whichprojects upward from the edge of this adjacent plank 10 to form alabyrinth seal. The walls 33, 34 enclose a gap 35 and interact in asealing manner in the same way as has been explained above withreference to FIG. 7. The cross-hatched areas indicate surfacereinforcement of those profiled-section parts which are exposed to highlevels of wear on account of their relative movement with respect to theopposite surfaces or beds of material. For the same reason, a strip 72,which forms a sealing gap with the end face of the wall 34 and islikewise reinforced, is provided beneath the wall 34 opposite its endface. Reinforcements of this type may also be provided in the otherembodiments of the sealing devices.

The design of the sealing device shown in FIG. 14 has the advantage oversome of the other sealing devices explained above that sealing surfaceswhich move to a lesser extent relative to one another are positionedopposite one another, and therefore the structural outlay and thefrictional energy which has to be applied are lower.

Details of a structure which is preferred for practical use can be seenfrom FIGS. 10, 11, 13. Horizontal, parallel longitudinal supports 40which bear the grate are arranged in the cooler housing. Brackets 41,which in each case bear bearing seats 42 for rollers 15, are secured tothem at predetermined longitudinal intervals. Rolling plates 44 whichare rigidly connected to side cheeks 46 of the planks 10 via transversesupports 45, rest on the rollers 15. Each plank 10 is supported by aplurality of rollers 15 arranged one behind the other. At least one ofthese rollers is driven in reciprocating fashion in order to impart theconveying movement described above to the plank, or else the planks aredriven directly by hydraulic piston-cylinder devices. There are devicesfor laterally guiding the planks, for example laterally running wheelflanges 43 at the rollers 15, which are matched to the width of therolling plates 44.

Transverse walls 13, between which the hollows 14 mentioned above areformed, are secured to the planks 10 at predetermined longitudinalintervals.

The gap between adjacent planks 10 is sealed by those parts 49 of theside cheeks 46 of the planks 10 which project above the planks having astationary sealing profile 47, which in cross section is in the form ofan inverted U shape and the lateral limbs of which form strips which areimmersed in the bed of material located on the planks in a similarmanner to the strips 34 in the exemplary embodiment illustrated in FIG.7, engaging over them. In terms of the sealing action, they cooperatewith those sections 49 of the side cheeks 46 which project above theplanks 10 and the arrangement and function of which corresponds to thewalls 33 of the exemplary embodiment shown in FIG. 7. The sealingprofile 47 is supported by holders 48 which project through between theplanks 10 and their adjacent side cheeks 46 and are supported by thelongitudinal supports 40.

The top-side seal produced by means of the sealing profiled section 47and illustrated in FIGS. 10 and 11 can be supplemented by an undersidesealing arrangement of the type illustrated in FIG. 7. This isillustrated in FIG. 12. It can be seen that the side cheeks 46, which atthe top side interact with the sealing profiled section 47 describedabove to form the seal arranged at the top side of the planks 10, towardthe bottom form strips 34 which are immersed in a channel 32 located atthe underside.

When viewing FIG. 10, it will be seen that it is readily possible forthe space beneath adjacent planks 10 to be separated by walls 50, whichare indicated by dot-dashed lines. In this case, the holder 48 will alsobe designed in a similar way to a continuous wall, so that no flowcommunication remains between the spaces 17 beneath adjacent planks 10.The separate spaces beneath the planks can if desired be acted on bydifferent pressures, in order to force difference quantities of coolingair through the layer of material located on the associated planks. Ifthe bed of material has different properties on adjacent planks, forexample different mean grain sizes or different bed heights or differenttemperatures, it is possible to take this into account bydifferentiating the air supply. For this purpose, cooling-air sourceswhich can be set differently are provided for the separate spaces 17.The grate according to the invention is particularly suitable for theabove-described separation of the spaces beneath the grate bylongitudinal partitions, since the longitudinal partitions can beconnected to the sealing members which continue in the longitudinaldirection between adjacent planks. It is also readily possible toprovide transverse walls in the space 17 beneath the grate, enablingsections which follow one another in the conveying direction to beventilated differently.

In FIG. 7, the air passage openings 12 in the base 38 of the planks 10can be seen as slots running transversely with respect to thelongitudinal direction. Beneath each slot 12 there is a catchingprofiled section 18, the downwardly facing edge 39 of which can be seenin FIG. 7.

As has been diagrammatically depicted in FIGS. 1, 4 and 5, the ends 20of the planks 10 pass beneath the feed section 4 in order to adjoin itwithout any gaps. To ensure that the air which is under excess pressuredoes not flow out of the space 17 beneath the grate through the gap 21between the top side of the plank part 20 and the underside of the feedsection 4 or to ensure that material does not pass into the space 17beneath the grate in the opposite direction to the conveying direction11, there is a sealing strip 22 which in the design variant shown inFIG. 4 tightly adjoins the end face of the grate section 4 arranged infront of it and is pressed onto the surface 24 of the plank end 20 byspring force 23. To ensure that the sealing strip 22 can be fittedtightly onto the top side 24, in the plank part 20 this top side isdesigned to be smooth without any hollows 14. This means that thesurface 24, when it is not directly beneath the feed section 4, isdirectly exposed to the wear caused by the still very hot material, andaccordingly has to be designed to be correspondingly resistant to hightemperatures and wear.

If it is desired to avoid this outlay, the alternative design shown inFIG. 5 comes into consideration, which is substantially equivalent tothat shown in FIG. 4 apart from the fact that the plank end 20, to theextent to which it may also be exposed to the hot material during theadvancing stroke, is also equipped with hollows 14 on the top side. Inthis case, the sealing strip 22 is mounted in a fixed position and itslower edge ends at a short distance above the walls 13 which enclose thehollows 14.

As long as the hollows 14 are located beneath the feed section 4, theyshould be cut off from the compressed air supply, otherwise there is arisk of some of the bulk material which is located in the hollows 14 andis required to protect the planks being blown out. The arrangementdescribed below with reference to FIGS. 5 and 7 is used for thispurpose. At least in the rear part 20 of the planks 10, the catchingprofiled sections 18 are surrounded by side cheeks 25. Beneath them, ina stationary position, there is a closure plate 28 which in theconveying direction 11 extends as far as the end of the feed section 4and in the opposite direction extends as far as a wall 29 by which thespace 17 beneath the grate is closed off to the rear and toward the sidewalls. The top side of the plate 28 is sealed off from the lower endfaces 26 of the side cheeks 25, for example by the plate 28 beingpressed onto the end faces 26 by spring force. In this way, the directadmission of compressed air from the space 17 beneath the grate to theair passage openings 12 is prevented as soon as these air passageopenings or the associated catching profiled sections 18 are locatedbehind the front edge of the plate 28. To prevent air from flowing outof the space beneath the grate, in the opposite direction to theconveying direction, between the top side of the plate 28 and thecatching profiled sections 18 to the air passage openings 12, transversewebs 37, which run down all the way as far as the top side of the plate28, are provided between successive catching profiled sections 18.Alternatively, it is also possible for the lower edges of the catchingprofiled sections 18 to interact in a sealing manner with the plate 28.

Should bulk material pass into the area below the feed section 4, it canbe collected outside the space 17 beneath the grate which is under anexcess pressure, in a collection chamber 30 (FIG. 5), from where it canbe sucked out continuously or from time to time.

As an alternative to the seal effected by the plate 28 beneath thegrate, it is also possible to provide a cover in the gap 21 above thegrate.

A further possibility for sealed connection of the grate section 5 tothe grate section 4 is shown in FIGS. 11 and 13. While the planks 10 aredesigned to be air-permeable with catching profiled sections in theregion of the hollows 14, as described above, the plank end, in theregion of the hollow 14′, is equipped with a closed base 55 which is notpermeable to air. Only this section of the plank which is not permeableto air moves under the grate section 4, thus obviating the lead toprovide a special closure plate (No. 28 in FIG. 5) which prevents theair from passing through. This section 55 of the plank which is notpermeable to air is protected from the influence of the high temperatureof the material coming off the grate section 4 by the material which hasbeen collected in the hollow 14′.

To seal the grate section 5 with respect to the grate section 4 there isa sealing arrangement which on the one hand beneath the grate section 4comprises a sealing plate 57 arranged parallel to the grate section 5and on the other hand at the rear end of each plank comprises a sealingdevice 56 which interacts therewith. The sealing plate 57, for which itis necessary to reckon with wear, is suspended in holes 59 in a bearingplate 60 by means of hooks 58 in such a manner that it can easily beexchanged and is fixed in the suspended position by means of a screw 61.After the screw 61 has been loosened, it can easily be removed andexchanged. The sealing device 56 at the rear end of the plank 10 moveswith the plank between two limit positions, the front one of which isindicated by continuous lines and the rear one of which is indicated bydot-dashed lines in FIG. 13.

The sealing device 56 comprises a U-profiled section 62 which is securedto the rear end of the air-impermeable plate 55 and between the limbs ofwhich the web 63 of a T-profiled section is guided moveably in a planewhich lies transversely with respect to the longitudinal direction ofthe plank 10. The flange 64 of the T-profiled section is pressed ontothe sealing plate 57 by a spring 65 in such a manner as to form a seal.

As can be seen most easily from FIG. 11, the T-profiled section 63, 64is divided in the center. The two parts are joined by a Z-joint 66, sothat a gap which is permeable to material is not formed even when thetwo parts move laterally apart. The two parts are each acted on by thespring 65 via inclined links 67 in such a manner that they are pressednot only upward onto the sealing plate 57 but also laterally outward. Asa result, their ends, which are likewise provided with a flange 68, arepressed onto the outer surfaces of the U-profiled section 47 describedabove with reference to FIG. 10. In this way, the hollow 14′, at itsrear end, is sealed both horizontally and vertically over its entirecross section with respect to the stationary parts 57 and 47. This sealis retained in each phase of the movement, since the sealing device 56moves with the plank. The sealing force by which the flange 64 bearsagainst the sealing surfaces of the plate 57 and of the profiled section47 is determined by the spring 65. The prestress of this spring can beset by means of the setscrew 69.

The embodiment illustrated in FIG. 11 assumes that the sealing gapsbetween adjacent planks are covered by a downwardly open U-shapedprofiled section 47 (cf. explanations given in connection with FIG. 10).The ends of the T-profiled sections 63, 64 are sealed against the sidefaces of these U-profiled sections. If the seal between adjacent planksis designed in the manner illustrated in FIG. 14, one end of theT-profiled section 63, 64 bears against the outer surface of the wall71, 34 of the adjacent plank where it forms a seal. A seal of this typeis not required at the other end of the T-profiled section.

Since the individual planks each move separately from the other planks,it is possible, by changing their stroke length or stroke frequency, toadjust their conveying influence which they exert on the material and inthis way to adjust the conveying speed of the material located on themseparately with respect to the other planks and/or the material locatedthereon. According to the invention, this fact is exploited through thefact that the selected properties of the material located on onespecific plank or a group of planks which may be of significance fordetermination of the conveying rate are measured by means of suitablesensors and the conveying speed of the plank (or more specifically: itsstroke frequency or stroke length or both) is influenced automaticallyas a function of these measurements. By way of example, the temperatureof the bed of material located on a plank is determined by radiationmeasurement of the surface of the bed of material or by measuring thetemperature of the cooling air which prevails immediately above thisbed, or alternatively a temperature profile across the width of thegrate can be determined at the cooler end by means of thermocouples orpyrometers. In this case, it is expedient to use in each case onemeasuring point per plank. The conveying speed of the plank can becontinuously controlled as a function of these measurements. If thetemperature rises, the speed is reduced, in order to lengthen theresidence time of the material in the cooling area, or vice versa. As analternative to continuous control, it is also possible to periodicallyreduce the speed if an increase in temperature is determined, and viceversa.

It is also possible to use this adjustment or control of the conveyingspeed in a targeted manner to combat specific undesirable operatingstates. Some materials tend to form hot flows, for example fine clinkertoward the edge (“Red River”), and this can be located by temperaturescanners and assigned to individual planks. Then, the stroke length (orthe stroke frequency or both) can be reduced by control technology meansfor the planks in question until the temperature profile has eveneditself out across the width of the grate. The reduction of the strokelength in the hotter zone causes the residence time of the combustionmaterial to increase in that zone and therefore makes the cooling ofthis material more intensive.

It will be clear that the invention makes it possible to achieve anydesired length of cooling grates without any friction losses withrespect to the grate occurring in the advancing stroke. Although duringthe return stroke there is some friction between the planks which areexecuting the return stroke and the bed located thereon, thereturn-conveying influence of these planks is low. This results inhighly efficient conveying of the material. The seal between adjacentplanks and/or the housing may be accommodated outside the hot area.There is also no need for conveying elements to be arranged within thehot area. The moving parts can be substantially protected from wear andthe influence of heat by material-trapping hollows. The stroke lengthcan be selected to be considerable, for example between 100 and 1000 mm,preferably between 300 and 600 mm. This results in a low strokefrequency and a correspondingly low level of wear and also a low load onthe drive members. The stroke length can be set differently across thewidth of the cooler in order to take account of different materialsproperties transversely across the width of the bed and in particular toavoid the Red River phenomenon in the clinker. It is possible to achievea uniform action of air over the width of the grate, since those regionsof known grates in which the air supply is blocked by sealing or driveelements are not present or at least can be reduced to a minimal size.The space beneath the grate can be divided by partitions in thetransverse and longitudinal directions, so that targeted ventilation,for example of the edge region, can be achieved even without the needfor flexible ventilation lines.

1-25. (canceled)
 26. An apparatus for cooling hot bulk material using acooling gas at a temperature lower than a temperature of the hot bulkmaterial, comprising: a grate comprising a plurality of separatelydriven adjacent planks which are elongate in the conveying direction,the grate being configured to convey a layer of the hot bulk materiallying on the grate from a feed end of the apparatus toward a deliveryend of the apparatus in a conveying direction and through which thecooling gas flows, the grate further comprising material-holdingrecesses on the surface of the grate which include air passage openings,a conveyance passage configured to convey the cooling gas into theapparatus so that the cooling gas passes from an underside of the grateto an upper side of the grate through the air passage openings andthrough the layer of hot bulk material on the grate, a drive moving theplanks forward and backward in an advancing stroke and a return strokein the conveying direction and controlling the motion of the planks insuch a way that the return strokes of adjacent planks take placenon-simultaneously and the advancing strokes of adjacent planks takeplace simultaneously.
 27. The apparatus of claim 26, wherein no conveyormembers lie above the grate.
 28. The apparatus of claim 26, comprisingstationary edge planks.
 29. The apparatus of claim 26, furthercomprising stationary intermediate planks between driven planks.
 30. Theapparatus of claim 26, further comprising sealing devices betweenadjacent planks.
 31. The apparatus of claim 26, further comprising asealing device between the planks and a side wall.
 32. The apparatus ofclaim 30, wherein the sealing device comprises a strip which isconfigured to penetrate into a layer of the bulk material.
 33. Theapparatus of claim 30, wherein the sealing device comprises alongitudinal channel beneath the grate which accommodates some of thebulk material.
 34. The apparatus of claim 32, wherein the strip isimmersed in a bed of material located on an adjacent plank and avertical wall is arranged at the adjacent plank engaging behind thestrip.
 35. The apparatus of claim 32, wherein a stationary sealingprofiled section having two strips is arranged in the conveyingdirection and is configured to be immersed in the layer of bulk materiallocated on two adjacent planks.
 36. The apparatus of claim 35, whereinthe stationary sealing profiled section is connected to a wall which isarranged between two planks and separates associated spaces beneath thegrate.
 37. The apparatus of claim 32, wherein the sealing device isventilated.
 38. The apparatus of claim 32, wherein the layer of materialis placed in a channel extending in the conveying direction and thelateral spacing between the strip and an adjacent channel walls isgreater than a lateral play of the plank or planks.
 39. The apparatus ofclaim 32, wherein the layer of bulk material is placed in a channelextending in the conveying direction and the lateral spacing between thestrip and an adjacent channel wall is greater than the vertical spacingbetween the strip and the bottom of the channel.
 40. The apparatus ofclaim 38, wherein the channel is open at the delivery end.
 41. Theapparatus of claim 38, wherein the channel is open at the feed end. 42.The apparatus of claim 26, wherein the feed end of the grate is coveredby a feed section which extends above the plane of the grate.
 43. Theapparatus of claim 42, further comprising a seal between the feedsection and the grate.
 44. The apparatus of claim 43, further comprisingmaterial-holding recesses provided in the feed end of the grate and theair passage openings in the material-holding recesses in the feed endare blocked off from the air supply in the region which is covered bythe feed section.
 45. The apparatus of claim 26, which is configured toreceive the material which is to be cooled by the apparatus from apreceding firing furnace and wherein at least a part of the cooling gas,after having passed the grate and the layer of material, is passed intothe firing furnace.
 46. The apparatus of claim 32, wherein the sealingdevice comprises a strip which penetrates into a layer of material. 47.The apparatus of claim 32, wherein the sealing device comprises alongitudinal channel, which accommodates some of the material, beneaththe grate